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Search Results: 1 - 10 of 2209 matches for " Takeshi Gonda "
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A Micromixer Using the Chaos of Secondary Flow: Rotation Effect of Channel on the Chaos of Secondary Flow  [PDF]
Yasutaka Hayamizu, Shinichiro Yanase, Shinichi Morita, Shigeru Ohtsuka, Takeshi Gonda, Kazunori Nishida, Kyoji Yamamoto
Open Journal of Fluid Dynamics (OJFD) , 2012, DOI: 10.4236/ojfd.2012.24A021
Abstract: The micromixer, which has a rotor with a curved channel, is studied experimentally. The secondary flow in a curved channel of rectangular cross-section is investigated using PIV (Particle Image Velocimetry) and LIF (Laser Induced Fluorescence) methods. Two walls of the channel (the inner and top walls) rotate around the center of curvature and a pressure gradient is imposed in the direction of the exit of the channel. The non-dimensional channel curvature δ=a/R is taken to be about 0.1, where 2a is the width of the channel, R the curvature radius of the channel. Other non-dimensional parameters concerned are the Dean number De=Reδ1/2, the Reynolds number Re=qdh/v, where q is the mean flow velocity in the channel axis direction, ν the kinematic viscosity, dh the hydraulic diameter of the channel, and the Taylor number Tr=2(2δ)1/2Ωa2/(δv), where Ω is the angular velocity of the rotor. Photographs of the flow in a cross-section at 180° downstream from the curved channel entrance are taken by changing the flux (De) at a constant rotational speed (Tr) of the channel walls. It is found that good mixing performance is obtained in the case of De≤0.1|Tr| and for that case secondary flows show chaotic behaviors. And then we have confirmed the occurrence of reversal of the mean axial flow.
Behavior of Motile Sperm in Taylor-Couette Flow: Effect of Shear Stress on the Behavior of Motile Sperm  [PDF]
Yasutaka Hayamizu, Toru Hyakutake, Koji Matsuura, Shinichiro Yanase, Shinichi Morita, Shigeru Ohtsuka, Takeshi Gonda
Open Journal of Fluid Dynamics (OJFD) , 2013, DOI: 10.4236/ojfd.2013.32A002
Abstract:

Infertility is often cited as one of the causes of a declining birthrate, which has become a serious social problem in recent years. Processes by which motile sperm can be safely and easily sorted are therefore important for infertility treatment. Therefore, as a new sorting method, microfluidic sperm sorter using the microfluidic system has been developed. To improve more separation efficiency of this device, it is necessary to know the behaviors of motile sperm in the microchannel where the sperm undergo shear flow. The previous study implied the necessity of the modeling of motile sperm in the shear flow. In the present study, therefore, we experimentally investigated the behavior of the motile sperm in the Taylor-Couette flow using PTV (Particle Tracking Velocimetry) method. The experimental results showed that the ascent of the shear stress led to the increase in the sperm velocity, and the direction of the sperm velocity was opposite to that of the flow.

A Micromixer Using the Taylor-Dean Flow: Effect of Inflow Conditions on the Mixing  [PDF]
Toshihiko Kawabe, Yasutaka Hayamizu, Shinichiro Yanase, Takeshi Gonda, Shinichi Morita, Shigeru Ohtsuka, Kyoji Yamamoto
Open Journal of Fluid Dynamics (OJFD) , 2014, DOI: 10.4236/ojfd.2014.45037
Abstract: Chaotic mixing in a curved-square channel flow is studied experimentally and numerically. Two walls of the channel (inner and top walls) rotate around the center of curvature and a pressure gradient is imposed in the direction toward the exit of the channel. This flow is a kind of Taylor-Dean flows. There are two parameters dominating the flow, the Dean number De (∝ the pressure gradient or the Reynolds number) and the Taylor number Tr (∝ the angular velocity of the wall rotation). In the present paper, we analyze the physical mechanism of chaotic mixing in the Taylor-Dean flow by comparing experimental and numerical results. We produced a micromixer model of the curved channel several centimeters long with square cross section of a few millimeters side. The secondary flow was measured using laser induced fluorescence (LIF) method to examine secondary flow characteristics. We also performed three-dimensional numerical simulations for the exactly same configuration as the experimental system to study the mechanism of chaotic mixing. It is found that good mixing performance is achieved for the case of De ≤ 0.1Tr, and that mixing efficiency changes according to the difference in inflow conditions. The flow is studied both experimentally and numerically, and both results agree with each other very well.
A Micromixer Using the Taylor-Dean Flow: Effects of Aspect Ratio and Inflow Condition on the Mixing  [PDF]
Yasutaka Hayamizu, Toshihiko Kawabe, Shinichiro Yanase, Takeshi Gonda, Shinichi Morita, Shigeru Ohtsuka, Kyoji Yamamoto
Open Journal of Fluid Dynamics (OJFD) , 2015, DOI: 10.4236/ojfd.2015.53027
Abstract: Chaotic mixing in three different types of curved-rectangular channels flow has been studied experimentally and numerically. Two walls of the channel (inner and top walls) rotate around the center of curvature and a pressure gradient are imposed in the direction toward the exit of the channel. This flow is a kind of Taylor-Dean flow. There are two parameters dominating the flow, the Dean number De (∝ the pressure gradient or the Reynolds number) and the Taylor number Tr (∝ the angular velocity of the wall rotation). In this paper, we analyze the physical mechanism of chaotic mixing in the Taylor-Dean flow by comparing experimental results and numerical ones. We produced three micromixer models of the curved channel, several centimeters long, with rectangular cross-section of a few millimeters side. The secondary flow is measured using laser induced fluorescence (LIF) method to examine secondary flow characteristics. Also we performed three-dimensional numerical simulations with the open source CFD solver, OpenFOAM, for the same configuration as the experimental system to study the mechanism of chaotic mixing. It is found that good mixing performance is obtained in the case of De ≤ 0.1 Tr, and it becomes more remarkable when the aspect ratio tends to large. And it is found that the mixing efficiency changes according to the aspect ratio and inflow condition.
沙质林地土壤阻抗系数测量方法
朱教君,徐大勇,康宏樟,gonda,yutaka,matsuzaki,takeshi
生态学杂志 , 2005,
Abstract: ?介绍了土壤阻抗系数的测量目的及测量的一般方法;重点描述了应用大地阻抗仪(yokogawatype3244)(specificearthresistancetester)测量沙质林地土壤阻抗系数的理论背景和室内、外操作步骤与数据处理方法.结果表明,使用3244大地阻抗仪,即运用wenner法测量沙质林地土壤阻抗系数是可行的,其测量结果在对土壤分层、确定表层土壤含水量、初步确定地下水位等具有一定的应用前景.
Een type van syntaktische spaarzaamheid
J. Gonda
Bijdragen tot de Taal-, Land- en Volkenkunde , 1950,
Abstract:
Some notes on the relations between syntactic and metrical units in a Javanese Kidung
J. Gonda
Bijdragen tot de Taal-, Land- en Volkenkunde , 1958,
Abstract:
Opmerkingen over Oud-Javaanse Zinsleer
J. Gonda
Bijdragen tot de Taal-, Land- en Volkenkunde , 1949,
Abstract:
Over Indonesische Werkwoordsvormen (II)
J. Gonda
Bijdragen tot de Taal-, Land- en Volkenkunde , 1949,
Abstract:
Prolegomena tot een theorie der Woordsoorten in Indonesische Talen
J. Gonda
Bijdragen tot de Taal-, Land- en Volkenkunde , 1949,
Abstract:
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